Andrew Wyeth, whose realistic yet often melancholy paintings of rural Pennsylvania and Maine made him one of America's most popular living artists, and whose 1948 landscape "Christina's World" was one of the 20th century's most famous artworks, died Friday. He was 91.

Wyeth died in his sleep at his home in Chadds Ford, Pa., southwest of Philadelphia, after a brief illness, the Brandywine River Museum said in a statement.

By 1950, he was being called a "master of the magic-realist technique" and lauded as one of the greatest American artists. Life magazine declared him "America's preeminent artist" in 1965, but an art world that increasingly embraced abstractionism seemed to take it as an insult.

When one art historian in 1977 was asked to name the most overrated and underrated artist of the century, he nominated Wyeth in both categories. Critics frequently disparaged Wyeth's watercolor and tempera landscapes and portraits as "painting with a camera" and said he was merely a Norman Rockwell wannabe, but Wyeth -- like Rockwell -- was popular with Middle America and inhabitants of the White House.

His works connected with the public because they expressed post-World War II optimism combined with the anxiety and disconnection people felt in the mid-20th century, David Brigham, museum director of the Pennsylvania Academy of Fine Arts, told Reuters news service.

Jim Duff, director of Chadds Ford's Brandywine River Museum, which houses many Wyeth paintings, called the artist "a man of extraordinary perception."

"He highly valued the natural world, the historical objects of this world as they exist in the present, and strong-willed people," Duff said in an Associated Press interview.

After “Christina’s World” was hung in 1948 in the Museum of Modern Art, it quickly became one of the New York City institution's most popular works. In it, dark-haired Christina Olson, a Maine neighbor who was crippled from the waist down, tries to drag herself through tawny grass toward a weathered farmhouse. The technical virtuosity of the painting and the haunting loneliness that the scene evokes proved to be hallmarks of Wyeth's style.

The public appeared to focus less on the painting's dark elements and more on the way Wyeth had painted each blade of grass -- realism that went against the abstract art movement that was gaining in America in the late 1940s.

In 1986, Wyeth attracted a hint of scandal when he revealed that he had secretly painted his neighbor, Helga Testorf, for 15 years. He insisted that not even his wife, Betsy, had previously seen the more than 240 paintings and drawings, many of them nudes. The large number of works and the palpable charge that runs through them suggested more than a simple artist-and-model relationship.

The Helga chapter landed on the covers of Time and Newsweek as the public speculated over whether Wyeth, then 69, had had an affair with the woman 22 years his junior. As the Wyeths tried to explain the relationship, the art world wondered whether the secrecy and subsequent revelation had been staged simply to raise the popularity and price of the paintings.

"It was a love affair with the burning love that I've always had toward the things I paint," Wyeth said of the Helga paintings. "If I don't have it, the painting goes ordinary, routine."

Leonard E.B. Andrews, a Pennsylvania publisher, bought the Helga collection in 1986 for a reported $6 million, and the National Gallery of Art in Washington, D.C., organized an exhibition of the pictures the next year. Andrews soon sold the Helga portfolio and other works to a Japanese collector for an estimated $45 million.

Stung by criticism over the "Helga hoopla," Wyeth denied there had ever been a sexual relationship, and his wife admitted that not all of the works had been kept secret from her. When critics accused the Wyeths, and Andrews, of being "hucksters," the artist verbally shrugged, saying critics "were just looking to bop me on the head."

During the height of the controversy, then-Los Angeles Times art critic William Wilson called Wyeth "a votive image of American traditionalism. . . . At best, Wyeth is sensitive, neurotic and accurate. His existence as an American phenomenon cannot be discounted."

Throughout his career of more than seven decades, Wyeth remained a figurative painter who prospered even when the genre was considered passe. He was tapped to paint a portrait of President Eisenhower for the cover of Time in 1959 and was given the nation's highest civilian honor, the Presidential Medal of Freedom, by President Kennedy in 1963. Wyeth was a favorite of President Nixon, who hosted a dinner and exhibit for him at the White House in 1970 and toasted him as an artist whose painting "has caught the heart of America."

On Friday, President Bush said Wyeth "captured America in his paintings." The president also pointed out that he and his father, President George H.W. Bush, had recognized Wyeth's contribution to American art and culture while in office.

Andrew Newell Wyeth was born July 12, 1917, in Chadds Ford, the youngest of five children of Newell Convers Wyeth and the former Carolyn Bockius. His father was also a noted artist, producing some 3,000 paintings and illustrating more than 110 books, including such classics as "Treasure Island" and "Kidnapped."